<template>
  <div>
    <h4>子组件--{{ value }}</h4>
    <button @click="changeNum">changeNum</button>
  </div>
</template>

<script>
export default {
  props: {
    value: {
      type: Number,
      default: 0
    }
  },
  methods: {
    changeNum() {
      this.$emit('input', 9)
    }
  }
}
</script>

<style>

</style>
